Stimulated Raman Adiabatic Passage via bright state in Lambda medium of unequal oscillator strengths

We consider the population transfer process in a Lambda-type atomic medium of unequal oscillator strengths by stimulated Raman adiabatic passage via bright-state (b-STIRAP) taking into account propagation effects. Using both analytic and numerical methods we show that the population transfer efficiency is sensitive to the ratio q_p/q_s of the transition oscillator strengths. We find that the case q_p>q_s is more detrimental for population transfer process as compared to the case where $q_p \leq q_s$. For this case it is possible to increase medium dimensions while permitting efficient population transfer. A criterion determining the interaction adiabaticity in the course of propagation process is found. We also show that the mixing parameter characterizing the population transfer propagates superluminally

Natural and anthropogenic forest fires recorded in the Holocene pollen record from a Jinchuan peat bog, northeastern China

Pollen and charcoal particles from a Jinchuan peat (northeastern China) were examined to investigate the fire origin and interaction between climate, vegetation, fire and human activity during the Holocene. Pollen results show that: (i) a broadleaved deciduous forest was dominant during the early Holocene; (ii) from ~5500 cal. yr B.P. there was a gradual increase in coniferous trees (mainly Pinus), and a decrease in broadleaved deciduous trees (e.g. Quercus, Juglans, and Ulmus–Zelkova); (iii) after ~4200 cal. yr B.P., the deciduous forest was replaced by a mixed forest of coniferous and deciduous trees; (iv) coniferous trees including Pinus, Abies and Picea further increased after ~2000 cal. yr B.P., reflecting a cooler and drier climate after ~5500–4200 cal. yr B.P. Two layers of abundant microfossil charcoal particles (250–10 μm) and the coexistence of macrofossil particles (N2 mm) suggest two local fires: fire event 1 (5120±66 cal. yr B.P.) and fire event 2 (1288±8 cal. yr B.P., AD 662±8). Charcoal layer 1, with a large amount of Monolete psilate spores, is superimposed on the long-term trend of vegetation changes, indicating a natural origin for fire event 1 that was probably facilitated by drying environmental conditions since the mid-Holocene. Cerealia-type pollen and a low percentage of Monolete psilate spores were observed in charcoal layer 2, indicating that fire event 2 was caused by clearing. We suggest that fire event 2 may be related to the spread of the Han farming culture accompanied by the territorial expansion of the Tang Dynasty to the studied area in AD 668

Influence of positional correlations on the propagation of waves in a complex medium with polydisperse resonant scatterers

We present experimental results on a model system for studying wave propagation in a complex medium exhibiting low frequency resonances. These experiments enable us to investigate a fundamental question that is relevant for many materials, such as metamaterials, where low-frequency scattering resonances strongly influence the effective medium properties. This question concerns the effect of correlations in the positions of the scatterers on the coupling between their resonances, and hence on wave transport through the medium. To examine this question experimentally, we measure the effective medium wave number of acoustic waves in a sample made of bubbles embedded in an elastic matrix over a frequency range that includes the resonance frequency of the bubbles. The effective medium is highly dispersive, showing peaks in the attenuation and the phase velocity as functions of the frequency, which cannot be accurately described using the Independent Scattering Approximation (ISA). This discrepancy may be explained by the effects of the positional correlations of the scatterers, which we show to be dependent on the size of the scatterers. We propose a self-consistent approach for taking this "polydisperse correlation" into account and show that our model better describes the experimental results than the ISA

Light hadron spectroscopy on the lattice with the non-perturbatively improved Wilson action

We present results for the light meson masses and decay constants as obtained from calculations with the non-perturbatively improved (`Alpha') action and operators on a 24^3 \times 64 lattice at beta = 6.2, in the quenched approximation. The analysis was performed in a way consistent with O(a) improvement. We obtained: reasonable agreement with experiment for the hyperfine splitting; f_K=156(17) MeV, f_pi =139(22) MeV, f_K/f_pi = 1.13(4) ; f_{K*}=219(7) MeV, f_rho =199(15) MeV, f_phi =235(4) MeV; f_{K*}^{T}(2 GeV) = 178(10) MeV, f_rho^{T}(2 GeV) =165(11) MeV, where f_V^{T} is the coupling of the tensor current to the vector mesons; the chiral condensate ^\bar{MS} (2 GeV)= - (253 +/- 25 MeV)^3. Our results are compared to those obtained with the unimproved Wilson action. We also verified that the free-boson lattice dispersion relation describes our results very accurately for a large range of momenta.Comment: 29 pages (LaTeX), 14 Postscript figure

Two minor determinants of myelin basic protein induce experimental allergic encephalomyelitis in SJL/J mice

Experimental allergic encephalomyelitis (EAE)' is an autoimmune inflammatory demyelinating disease in the central nervous system (CNS) of animals immunized with myelin basic protein (MBP). The disease is directly mediated by Thelper cells that recognize MBP in the context ofclass II antigens of the MHC (1-3). In nude mice, a single clone of adoptively transferred MBP-reactive T helper cells can cause EAE (4), suggesting that these are the only T cells required for disease induction. As a prototypic model of T helper cell-mediated autoimmune disease, observations in EAE could likely be applicable to other T helper cell-mediated diseases such as murine lupus (5), thyroiditis (6), collagen arthritis (7), and adjuvant arthritis (8), as well as human autoimmune diseases. The MBP epitope is determined in part by the MHC. Using proteolytic peptide fragments of MBP, SJL/J (H-2s) and BIO.T(6R) (H-2q) mice were found to develop EAE to the COOH-terminal peptide of MBP, whereas PL/J (H-2u) and A/J (H-2k) mice developed EAE to the NH2-terminal peptide of MBP (9). Recently, by using synthetic peptides that overcome the difficulties of obtaining pure uncontaminated proteolytic peptides, a single T cell encephalitogenic epitope for PL/J mice has been identified . This epitope consists of the first nine NH2-terminal amino acid residues of MBP which must be acetylated at the a amino group to induce disease (10). Similar fine mapping of the encephalitogenic T cell epitope(s) for SJL/J mice has not been done, in part because of the large size of the COOH-terminal peptic fragment of MBP (residues 89-169 of rat MBP, reference 9). MouseMBP consists offour major forms due to differential RNA splicing of exons II and VI (11), resulting in molecular masses of 21, 18.5, 17.5, and 14 kD, in the relative amounts of 1 :10:3.5:35 . Since EAE can also be induced with the small form of rat MBP (14 kD), which has exons II and VI of the MBP gene deleted (12), the COOH-terminal encephalitogenic determinant for SJL/J mice must be present within a segment ofonly 42 amino acid residues . Consistent withthis notion is the observation that this peptide sequence is identical among the MBPs of several mammalian species, including mouse, rat, bovine, guinea pig, and porcine, all of which can induce EAE in SJL/mice (13, 14). To identify the SJL/J encephalitogenic T cell epitope(s), overlapping peptides to the COOH-terminal region ofthe small form of mouse MBP were synthesized. Two overlapping peptides encompassing an 18-amino acid region were found to elicit EAE in SJL/J mice. The finding of a single peptide region of MBP that is responsible for encephalitogenic T cell epitopes in SJL/J mice is analogous to that of the PL/J mice and has implications for the development of specific therapy for T cell-mediated autoimmune diseases

Thermal Ground Testing of Concorde and Veras or Improvement in French Test Methods and Facilities

The more numerous the requirements are in aerospace vehicle operations, the more the ground test facility have to improve both the nature and the quality of the equipment as well as the volume and the size of the sites, for the importance of ground testing cannot be over emphasized. As an example, two ground test programs are reviewed in this presentation, namely CONCORDE and VERAS. Special emphasis is given to the facility implementations due respectively to the static and fatigue test of CONCORDE in heat environment and to the dynamic test of VERAS in high level and transient temperature conditions

Phonon runaway in nanotube quantum dots

We explore electronic transport in a nanotube quantum dot strongly coupled with vibrations and weakly with leads and the thermal environment. We show that the recent observation of anomalous conductance signatures in single-walled carbon nanotube (SWCNT) quantum dots can be understood quantitatively in terms of current driven `hot phonons' that are strongly correlated with electrons. Using rate equations in the many-body configuration space for the joint electron-phonon distribution, we argue that the variations are indicative of strong electron-phonon coupling requiring an analysis beyond the traditional uncorrelated phonon-assisted transport (Tien-Gordon) approach.Comment: 8 pages, 6 figure

Magnetohydrostatic solar prominences in near-potential coronal magnetic fields

We present numerical magnetohydrostatic solutions describing the gravitationally stratified, bulk equilibrium of cool, dense prominence plasma embedded in a near-potential coronal field. These solutions are calculated using the FINESSE magnetohydrodynamics equilibrium solver and describe the morphologies of magnetic field distributions in and around prominences and the cool prominence plasma that these fields support. The equilibrium condition for this class of problem is usually different in distinct subdomains, separated by free boundaries, across which solutions are matched by suitable continuity or jump conditions describing force balance. We employ our precise finite element elliptic solver to calculate solutions not accessible by previous analytical techniques with temperature or entropy prescribed as free functions of the magnetic flux function, including a range of values of the polytropic index, temperature variations mainly across magnetic field lines and photospheric field profiles sheared close to the polarity inversion line. Out of the many examples computed here, perhaps the most noteworthy is one which reproduces precisely the three-part structure often encountered in observations: a cool dense prominence within a cavity/flux rope embedded in a hot corona. The stability properties of these new equilibria, which may be relevant to solar eruptions, can be determined in the form of a full resistive MHD spectrum using a companion hyperbolic stability solver.Comment: To appear in ApJ August 200

New results from APE with non-perturbatively improved Wilson fermions

We present the results for light hadron spectrum, decay constants and the quark masses obtained with non-perturbatively improved Wilson fermions. We also give our preliminary results for the heavy-light decay constants.Comment: 3 pages, 2 figures, corrected some typos and one reference added, LATTICE98(spectrum

Promoting Climate-Friendly Diets: What Should We Tell Consumers in Demark, Finland and France?

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